#define _CRT_SECURE_NO_WARNINGS 1


#include "Stack.h"

void STInit(ST* ps)
{
	assert(ps);

	ps->a = NULL;
	ps->top = 0;//top指向栈顶元素的下一个
	//ps->top = -1;//top指向栈顶元素
	ps->capacity = 0;
}

void STDestroy(ST* ps)
{
	assert(ps);

	free(ps->a);
	ps->a = NULL;
	ps->top = ps->capacity = 0;
}

//栈顶
void STPush(ST* ps, STDataType x)
{
	assert(ps);

	//满了，扩容
	if (ps->top == ps->capacity)
	{
		int newcapacity = 0 == ps->capacity ? 4 : 2 * ps->capacity;
		STDataType* tmp = (STDataType*)realloc(ps->a, newcapacity * sizeof(STDataType));

		if (NULL == tmp)
		{
			perror("realloc fail");
			return;
		}

		ps->a = tmp;
		ps->capacity = newcapacity;
	}

	ps->a[ps->top] = x;
	ps->top++;
}

void STPop(ST* ps)
{
	assert(ps);
	assert(!STEmpty(ps));

	ps->top--;
}

STDataType STTop(ST* ps)
{
	assert(ps);
	assert(!STEmpty(ps));

	return ps->a[ps->top - 1];
}

int STSize(ST* ps)
{
	assert(ps);

	return ps->top;
}

bool STEmpty(ST* ps)
{
	assert(ps);

	return 0 == ps->top;
}